Access

Letter

Nature 454, 81-83 (3 July 2008) | doi:10.1038/nature07068; Received 16 March 2008; Accepted 1 May 2008

Open Innovation Challenges

naturejobs

Domination of heliosheath pressure by shock-accelerated pickup ions from observations of neutral atoms

Linghua Wang1,2, Robert P. Lin1,2, Davin E. Larson2 & Janet G. Luhmann2

  1. Physics Department, University of California, Berkeley, California 94720-7300, USA
  2. Space Sciences Laboratory, University of California, Berkeley, California 94720-7450, USA

Correspondence to: Linghua Wang1,2 Correspondence and requests for materials should be addressed to L.W. (Email: windsound@ssl.berkeley.edu).

Top

The solar wind blows an immense magnetic bubble, the heliosphere, in the local interstellar medium (mostly neutral gas) flowing by the Sun1. Recent measurements by Voyager 2 across the termination shock, where the solar wind is slowed to subsonic speeds before entering the heliosheath, found that the shocked solar wind plasma2 contains only approx20 per cent of the energy released by the termination shock, whereas energetic particles3 above approx28 keV contain only approx10 per cent; approx70 per cent of the energy is unaccounted for, leading to speculation2, 3 that the unmeasured pickup ions or energetic particles below 28 keV contain the missing energy. Here we report the detection and mapping of heliosheath energetic (approx4–20 keV) neutral atoms produced by charge exchange of suprathermal ions with interstellar neutral atoms. The energetic neutral atoms come from a source approx60° wide in longitude straddling the direction of the local interstellar medium. Their energy spectra resemble those of solar wind pickup ions, but with a knee at approx11 keV instead of approx4 keV, indicating that their parent ions are pickup ions energized by the termination shock. These termination-shock-energized pickup ions contain the missing approx70 per cent of the energy dissipated in the termination shock, and they dominate the pressure in the heliosheath.

  1. Physics Department, University of California, Berkeley, California 94720-7300, USA
  2. Space Sciences Laboratory, University of California, Berkeley, California 94720-7450, USA

Correspondence to: Linghua Wang1,2 Correspondence and requests for materials should be addressed to L.W. (Email: windsound@ssl.berkeley.edu).

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.

NEWS AND VIEWS

Solar System A shock for Voyager 2

Nature News and Views (03 Jul 2008)

Cometary science: ICE encounters Giacobini?Zinner

Nature News and Views (03 Oct 1985)

See all 5 matches for News And Views